1. Field of the Invention
The present invention is generally in the field of electronic devices. More particularly, the invention is in the field of battery and power management for electronic devices.
2. Background Art
Many modern electronic devices that are powered by a battery implement some method of monitoring the battery to estimate battery run time. For example, cellular telephones, portable music players, digital cameras, and other devices each typically include a circuit or subsystem implementing a method for monitoring the battery included in the device. Presently, two methods are typically used. The first method measures the battery voltage to estimate the battery run time, while the second method tracks the charge applied to and taken from the battery to estimate the battery run time. Both methods have attendant drawbacks.
For example, the first method, which monitors battery voltage, is inaccurate and only provides rough estimation for battery run time, because the relationship between battery voltage and battery capacity varies according to the load placed on the battery by the device. The load placed on the battery typically varies dynamically, thus making battery capacity and run time estimation difficult. The second method, which tracks the charge applied to and taken from the battery, can in some cases generate more accurate run time estimates than the first method. However, circuits or subsystems implementing the second method tend to be more expensive. Also, such circuits or subsystems are implemented in the battery of a device, instead of in the device itself, because otherwise tracked charge will become inaccurate when batteries are replaced. Furthermore, this method can suffer inaccuracies when tracked batteries are not deeply discharged and then fully charged.
Thus, there is a need in the art for a method for accurate battery run time estimation that overcomes the disadvantages associated with utilizing conventional methods.